Activity, Performance, and Durability for the Reduction of Oxygen in PEM Fuel Cells, of Fe/N/C Electrocatalysts Obtained from the Pyrolysis of Metal-Organic-Framework and Iron Porphyrin Precursors. (20th March 2015)

• Record Type: Journal Article
• Authors: Yang, Lijun; Larouche, Nicholas; Chenitz, Régis; Zhang, Gaixia; Lefèvre, Michel; Dodelet, Jean-Pol
• Is Part Of: Electrochimica acta. Volume 159(2015)
• Page Start: 184
• Page End: 197
• Publication Date: 2015-03-20
• Subjects: Catalyst -- O2 reduction -- Proton Exchange Membrane Fuel Cell -- ZIF-8 -- ClFeTMPP; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2015.01.201
• Languages: English
• ISSNs: 0013-4686

Abstract

Graphical abstract: TOC After a first decay common to all electrocatalysts, only NC Por_0.8 -1150 Ar + NH3 shows an improvement in durability attributable to a decrease in water flooding its catalytic sites, particularly those located in micropores. Abstract: Fe/N/C type catalysts have been produced by ballmilling ZIF-8 (a metal-organic-framework) and a chloroiron-tetramethoxyporphyrin (ClFeTMPP). The resulting material was first pyrolyzed in Ar at temperatures ranging from 850 to 1150 °C, then in NH3 at 950 °C in order to produce two series of catalysts: the Ar and the Ar + NH3 ones. They were labeled NC Por_x-T Ar or NC Por_x-T Ar + NH3, where x is the nominal Fe loading in wt% and T is the temperature of the first pyrolysis in Ar. At 80 °C in H2 /O2 fuel cell, the most active and performing catalyst is NC Por_0.8-1050 Ar + NH3 . All NC Por_0.8-T Ar + NH3 catalysts with T comprised between 850 and 1050 °C display the same instability behavior. The only catalyst showing an improvement in durability is NC Por_0.8-1150 Ar + NH3 . It is proposed that the drastic change in durability upon increasing the first pyrolysis temperature, from 1050 to 1150 °C in Ar, is attributable to an important decrease in the heteroatom content (a drop of 32% for both N and O atoms) of the catalyst upon graphitization, reducing the hydrophilic character of its carbonaceous support and decreasing the possibility of water flooding its catalytic sites, particularly the sites located in micropores.